1. Field of the Invention
The present invention relates to a fixing structure for a rotor, and, more particularly, to a rotor of a brushless motor that can be detached and assembled easily.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a conventional brushless motor comprising a casing 90 with an axle seat 91 for mounting an axle tube 92. Mounted around an outer periphery of the axle tube 92 are a circuit board 93 and a stator bobbin 94. The axle tube 92 includes a bearing mounted to an inner periphery thereof for rotatably holding a shaft 96 of a rotor 95. The shaft 96 includes an annular groove 97 for engaging with a C-clip 98.
In assembly, the axle tube 92 is extended through the circuit board 93 and the stator bobbin 94 and then engaged with the axle seat 91 of the casing 90, and the shaft 96 of the rotor 95 is extended through the bearing in the axle tube 92 and then retained in place by means of engaging the C-clip 98 into the annular groove 97 of the shaft 96. Thus, the rotor 95, circuit board 93, and stator bobbin 94 together constitute a brushless motor.
However, as illustrated in FIG. 2, mounting of the C-clip 98 into the annular groove 98 of the distal portion of the shaft 96, so that a side of the C-clip 98 presses against an end face of the bearing, is difficult because the distal portion of the shaft protrudes only slightly beyond the bearing in the axle tube 92. It was found that about 20%xcx9c30% of the brushless motors cannot pass the quality test after assembly, and the rejected brushless motors must be detached and retested and/or have their elements replaced. The first step of detachment is to remove the C-clip 98 from the annular groove 97 of the shaft 96, and the C-clip 98 is thus damaged and cannot be used. In conclusion, detachment and assembly for such a conventional brushless motor is difficult and troublesome, and a C-clip is damaged in each detaching procedure. In addition, the C-clip 98 securely engaged in the annular groove 97 of the shaft 96 rotates together with the shaft 96 and thus generates noise as the C-clip 98 and the bearing would have friction therebetween.
It is the primary object of the present invention to provide a fixing structure for a rotor to allow easy assembly and detachment and to reduce rotational noise of the rotor.
A brushless motor in accordance with the present invention comprises a casing including an axle seat with an axle hole, the axle hole having a flange provided therein. An axle tube is engaged on the axle seat and includes a bearing mounted therein for rotatably holding a shaft of a rotor. The shaft includes a distal end that extends beyond an end face of the bearing, the distal end including a neck to thereby define an annular groove. An engaging member is mounted in the axle hole of the axle seat and retained in place by the bearing or the axle tube. The engaging member includes a hole having an inner diameter smaller than a diameter of the shaft of the rotor. An inner peripheral wall defining the hole of the engaging member includes a plurality of notches to thereby allow forcible passage of a distal end of the shaft through the hole of the engaging member. The peripheral wall of the hole of the engaging member is located in the annular groove of the shaft after the distal end of the shaft is passed through the hole of the engaging member.
Other objects, specific advantages, and novel features of the invention will become more apparent from the following detailed description and preferable embodiments when taken in conjunction with the accompanying drawings.